1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device by an elevated source/drain technology which forms a silicon layer on a source/drain region by selective epitaxial growth.
2. Related Art
In elevated source/drain technology, a single-crystal silicon layer is formed by epitaxial growth on a source/drain region formed in a semiconductor substrate, then a suicide reaction takes place on the silicon layer, and thus forms a silicide layer on the semiconductor substrate. This process enables an impurity layer of the source/drain region to be shallower, and thereby contributes to the miniaturization of elements.
Referring to the elevated source/drain technology, the technology generally requires heat treatment reaching a temperature of 700° C. or higher in a process forming silicon by epitaxial growth. Consequently, an impurity profile in the source/drain region previously formed by ion implantation is changed, which may make it difficult to suit an impurity profile requested by design specifications.
In addition, when using a metal gate, performing the above-mentioned heat treatment of 700° C. or higher after forming the metal gate can deteriorate the properties of a gate insulating layer, as a result of a surface reaction between a material of the metal gate and a material of the gate insulating layer.
An object of the present invention is to provide a method for manufacturing a semiconductor device which can form a highly controlled impurity layer without influence from the above-mentioned heat treatment in the process of epitaxial growth.